[RSR]

Originally Posted by wooka

1. No Diag lights so far. Bulbs are working fine.

2. The one after the cat con will also need to be checked, right?

3. Unplugging will make the O2 sensor read lean? So the mix will get richer and cooler and not knock. This is definitely going to fix it, right? Since I believe the ECM will try to maintain a 50% lean \ rich mixture ratio. I could be wrong, and probably am, please correct me here.

4. 7K this is something I will use a salvaged part for and not pay that much. Am not paid barely enough. Plus I'd rather stomach the mild knocking and cycle to work

5. Clogged would be loaded with carbon? If so, an ultrasonic or chemical bath/ abrasives -- which is the best way out?

1) No CEL or MIL indication? If it light up, then it would have been easier to troubleshoot with the help of an error code. But yes, a faulty/clogged O2 sensor may not necessarily set an error code.

2) Yes! Although the upstream O2 sensor is the one that generally causes trouble first, it wouldn't hurt to check the downstream sensor as well.

3) True. Unplugging it will cause it to run in open loop with a richer mixture. This can lead to increased performance. I was able to actually feel the difference, like the engine gained half-a-dozen horses and a couple of kg.m, but then .

However, running with the O2 sensor permanently unplugged is not recommended! It will lower fuel efficiency, and worse, may damage components like the cat-con etc. So please unplug it only temporarily for diagnostic purposes.

If something else is causing the knocking, then tinkering with the O2 sensor wouldn't work, of course. Using a diagnostic scanner is recommended for easier troubleshooting.

4) 7k is indeed expensive! The upstream O2 sensor went kaput in two-and-a-half years for me, and the workshop wanted me to foot the bill for a replacement as the 2-year warranty was over. I finally managed to get them replace it under the emission warranty (which is valid for 3-years or 80,000 km).

5) Yes, the deposits have to be removed in a careful cleaning process.

I've heard different methods of cleaning an O2 sensor. One is to use a flame to burn off the carbon deposits, though this can be tricky. Another is to keep it soaked in gasoline overnight, then blow it clean and repeat the process. I've even come across people mentioning they used white vinegar, though I don't know how effective it would be.

I'll hook up my small scanner to the engine and see if it gives any O2 sensor operating parameters. I'll let you know this evening.

Originally Posted by wooka

6. Thanks for sharing and helping a nuble out.

You're welcome! I'm not an expert myself, but then this is what a forum is all about - learning from each other's experiences.

[wooka]

Hi on the tablet so can't quote edit very well..

In a nutshell, removed the O2 sensor and no results. I can tell you this much - knocking is worse. I might be hearing things but it seems as if it's okay in a cold engine and gets worse when hot? ( possible or am I mushy headed)

HSS will have to wait as they've told me to empty my fuel tank, get my fuel filter changed and get oil from a fresh pump =/

Not one person is chandigarh seems to have an endoscope to look inside the cylinder. My garage guy says the Desi compression testing instruments are worth not their weight in scrap. Power balance test and ignition pattern test can now happen at HSS only.

No error codes on the generic ebd port. Hope HSS can do better.

Lastly, my mechanic says it's 90% a problem with the timing belt or head gasket. But that's not only expensive to replace, but every time it's opened it has to be replaced.. So if the cylinder has the problem and we look there too late (after gasket head changing) then I'm going to have to buy yet another gasket head. He says it's never going to fit quite right. And if I am doing the gasket heads it's worth opening the cylinders. He might as well take my engine home =#

Timing belt will cost me 2k but 1.5k if I use an OEM tensioner, and not Hyundai. Giving the potential damages to sort out this issue, every but counts. Worth it?
And finally, I have further concluded that the knocking is apparent every time I slam the accelerator and then is intermittent. Every few seconds. Regardless of gear but most audible in the 3rd and 4th.

Edit : My mileage is about 15 chandigarh city so that's not much of a challenge. It hasn't dropped that low so as to believe low compression is a culprit?

[RSR]

Originally Posted by RSR

I'll hook up my small scanner to the engine and see if it gives any O2 sensor operating parameters. I'll let you know this evening.

I'm so sorry for the delay in replying, wooka .

I did hook up the scanner, and here are the results.

There are two O2 sensors, and the scanner provides live data (voltage readings) through the OBD II port (Hyundai seems to use CAN protocol in most of their cars).

The first O2 sensor's readings (I presume this is the upstream sensor, just after the exhaust manifold) varied continually from ~ 0.075 to ~ 0.9 volts and it was varying so fast, that I could not get the exact readings of the two extremes of the range.

The second O2 sensor's reading (I presume this to be the downstream sensor, just after the cat-con) on the other hand, remained rock solid at exactly 0.455 volts!

I understand that the voltage readings correspond to a % of the fuel mixture, and it can theoretically vary from 0 volts which corresponds to -100 (on the lean side) to 1.275 volts which corresponds to 99.2 (on the rich side). But what does the varying nature of the first reading, and the steady nature of the second indicate? Is this supposed to be normal?

Originally Posted by wooka

In a nutshell, removed the O2 sensor and no results. I can tell you this much - knocking is worse.

I think the O2 sensor readings are not going to be of much help anyway, as you have already tested it, and found that it is not the culprit.

Originally Posted by wooka

No error codes on the generic ebd port. Hope HSS can do better.

I think you can give a Hyundai workshop a try. They have a manufacturer specific diagnostic service tool that performs all functions and is nicknamed the Hi-Scan. I think it provides a live graph for several parameters and the Hyundai technicians can compare it to standard graphs to see if something is wrong with some component - this is quite difficult with a generic OBD scanner (on some advanced generic ones it should be possible, though).

Before you open up the engine to do the expensive stuff, you can also search for a very experienced mechanic (not necessarily at a Hyundai workshop) in your city who knows his stuff and ask his opinion about the knocking. The Epsilon/iRDE engine is quite common, and has been around for a long time. Any skilled troubleshooting expert should be able to easily identify what's causing this problem if he has dealt with a similar thing in the past.

[joybhowmik]

Originally Posted by wooka

Thanks joybhowmik,

Will wait till thursday, my trip to the mech, and will post back.

Still, for the O2 sensors, what voltage range am I looking at, and how can they possibly be cleaned?

From the service manual it appears to be 0-1V.

There is no guidance on sensor cleaning. However do refer the following trouble shooting guides to get a better understanding of the step by step process as recommended by Hyundai.

[joybhowmik]

Originally Posted by wooka

Lastly, my mechanic says it's 90% a problem with the timing belt or head gasket.

Wooka - your mechanic seems to have gone soft in the head. Ask him to tie the timing belt from a tree, place his neck in it, and hang!
If engine knocking, and hesitant starts is a timing belt issue, then people would have changed out their timing belt far sooner than one thinks possible. Failure of timing belt (its breakage) only means one thing - the camshaft goes out of sync with the crankshaft. And before you can complete reading this sentence, the engine will have catastrophically seized.

Why would replacing the head gasket , involve your mechanic taking the engine home - is he into doing homework at an advanced age?
It's just a gasket - think of the equivalent pressure cooker gasket. Broadly - to get at it, remove the timing belt, disconnect all connections from the head, remove valve cover on the head, Loosen the torqued fasteners between the head and cylinder in the way specified by Hyundai, and gently remove the head. Then scrape off the old gasket, clean the mating surfaces and put a new gasket in with the prescribed sealant. Prima facie it does not appear that there is a blown gasket problem per se... you have not reported any loss of engine oil, nor any obvious loss in engine coolant levels or steamy exhaust. Ideally removing the head and changing the gasket is not more than 2 - 3 hours of work provided the person doing the job is experienced. At the going rate of labour @ ~ Rs 250/- per hour you can do the maths.
It's just because you mentioned your mechanic advised that the gasket requires some homework, that I thought to set the record straight.